The present invention relates to a process for producing a polymer. More particularly, the invention relates to a polymer suitably used for an interlayer dielectric for semiconductor devices and the like, a process for producing the same, an insulating-film-forming composition, an insulating film, and a method of forming the same.
A silica (SiO2) film formed by a vacuum process such as chemical vapor deposition (CVD) has been widely used as an interlayer dielectric for semiconductor devices and the like. In recent years, a coating-type insulating film called a spin-on-glass (SOG) film, which contains a tetraalkoxysilane hydrolyzate as the major component, has also been used in order to form an interlayer dielectric with a more uniform thickness. Along with an increase in the degree of integration of semiconductor devices, a low-relative-dielectric-constant interlayer dielectric called an organic SOG film, which contains a polyorganosiloxane as the major component, has been developed.
Since the degree of integration and the number of layers of semiconductor devices have been further increased, an improved electrical insulation between conductors has been demanded. Therefore, an interlayer dielectric exhibiting excellent storage stability, a lower relative dielectric constant, and excellent leakage current characteristics has been in demand.
JP-A-2001-127152 proposes a method which includes preparing a coating liquid by mixing a polycarbosilane solution and a polysiloxane solution and forming a low-dielectric-constant insulating film using the resulting coating liquid. However, this method has a problem in which the carbosilane domains and the siloxane domains are nonuniformly dispersed in the resulting coating. A semiconductor device manufacturing process involves a chemical mechanical planarization (CMP) step for planarizing an insulating layer and various cleaning (washing) steps. Therefore, a material used for an interlayer dielectric or a protective film for semiconductor devices is required to exhibit mechanical strength and chemical resistance against chemical corrosion in addition to the dielectric constant characteristics.